Diuretics are an important cause of symptomatic hyponatraemia in the elderly. The hyponatraemia is often associated with hypokalaemia which may play a role in the aetiology. Diuretic induced hyponatraemia must be considered in the differential diagnosis of elderly patients presenting with altered sensorium or seizures. This is especially important in those known to be hypertensives since diuretics are frequently used to treat hypertension in the elderly.